Systemic lupus erythematosus is a chronic relapsing autoimmune disease that involves multiple organ systems. The etiology and pathogenesis of lupus are incompletely understood. There is a strong evidence for genetic contribution to the pathogenesis of lupus, however, despite the enormous progress in mapping lupus susceptibility genes, only a small fraction of lupus heritability is accounted for by the genetic associations discovered. A large body of literature supports the contention that epigenetic dysregulation, particularly T cell DNA methylation defect, contributes to the pathogenesis of lupus. Indeed, demethylated T cells are sufficient to cause lupus in animal models. We believe that epigenetic differences between lupus patients and controls contribute towards the missing heritability of the disease. We propose to determine and functionally characterize differentially methylated genetic loci in specific T cell subsets in lupus patients compared to normal controls, using a genome-wide approach, the feasibility of which has been confirmed in our own preliminary experiments. We will further Identify and validate DNA methylation changes over time in relation to disease activity in lupus patients. We hypothesize that genetic variants associated with lupus will alter DNA methylation in known lupus susceptibility loci in an allele-specific manner. Therefore, we will determine allele specific DNA methylation changes in validated genetic susceptibility loci for lupus. We previously reported the genetic association between SNPs within MECP2 and lupus. MECP2 (methyl-CpG-binding protein 2) is a key transcriptional regulator for methylation sensitive genes, and is also known to recruit the DNA methylation enzyme DNMT1 during DNA synthesis. We will resequence the MECP2/IRAK1 LD block using next generation sequencing to identify the causal variants in this locus.